Optical recording system with a built-in jitter detector

ABSTRACT

An optical recording system for burning an optical disc includes a housing, a laser pickup installed inside the housing for writing data onto the optical disc according to a write strategy and reading an RF signal from the optical disc, a laser drive connected to the laser pickup for controlling operations of the laser pickup, a read channel installed connected to the laser pickup for processing the RF signal received by the laser pickup, a jitter meter installed inside the housing connected to the read channel for generating delay signals according to the processed RF signal, and a digital signal processor connected to the laser drive and the jitter meter for receiving the delay signals, configuring the write strategy according to the delay signals, and controlling the laser drive to control the laser pickup to write data onto the optical disc according to the configured write strategy.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention provides an optical recording system, and moreparticularly, an optical recording system which has a built-in jittermeter.

2. Description of the Prior Art

Data are written onto an optical disc with 3T to 11T pulse trains. AllCD-R/RW drives use Optimum Power Control (OPC) to set the laser powerfor a specific disc type. Vendor supplied information in the ATIP(vendor, dye type, maximum recording length, supported write speeds,etc.), is used to set the initial “best guess” laser power. A test burnin a reserved area of the disc using power levels in a wide range aboveand below this initial setting, and analysis of the test burn, resultsin an ‘optimum’ setting for the recording using one of those levels.However, the “optimum” setting may not always be optimal because thewrite strategy may be different for writing data onto different portionof the same disc and for writing data with different length of pulsetrains.

Please refer to FIG. 1. FIG. 1 is a flowchart of a related art methodfor configuring a write strategy. In step 1, the optical recorder isprovided with a write strategy. In step 3, a test burn is performed towrite test data onto a disc. In step 5, the test data is read from thedisc and evaluated to check the burning quality. If the test data hasacceptable quality, then perform step 7 to configure the write strategyused for burning the test data as the write strategy for burning formaldata. If the test data has unacceptable quality, then perform step 9 toreconfigure the write strategy and repeat step 3 until the test data hasacceptable quality.

It can be seen that the write strategy has to be fine-tuned severaltimes before an acceptable write strategy can be configured. Further,the signal quality needs to be evaluated with an externally connectedtest equipment or jitter. The externally connected test equipment orjitter is very expensive and requires professional skill to operate. Anordinary user cannot possibly operate such equipment to configure thewrite strategy for an optical disc.

SUMMARY OF INVENTION

It is therefore an objective of the present invention to provide anoptical disc system which has a built-in jitter meter to solve the abovementioned problems.

According to the claimed invention, the optical recording system forburning an optical disc comprises a housing, a laser pickup installedinside the housing for writing data onto the optical disc according to awrite strategy and reading an RF signal from the optical disc, a laserdrive installed inside the housing connected to the laser pickup forcontrolling operations of the laser pickup, a read channel installedinside the housing connected to the laser pickup for processing the RFsignal received by the laser pickup, a jitter meter installed inside thehousing connected to the read channel for generating delay signalsaccording to the processed RF signal, and a digital signal processorinstalled inside the housing connected to the laser drive and the jittermeter for receiving the delay signals, configuring the write strategyaccording to the delay signals, and controlling the laser drive tocontrol the laser pickup to write data onto the optical disc accordingto the configured write strategy.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart of a related art method for configuring a writestrategy.

FIG. 2 is a functional block diagram of an optical disc system accordingto the present invention.

FIG. 3 is a block diagram of the jitter meter in FIG. 2.

FIG. 4 is a timing diagram of the jitter meter in FIG. 2.

DETAILED DESCRIPTION

Please refer to FIG. 2. FIG. 2 is a functional block diagram of anoptical disc system according to the present invention. The optical discsystem comprises a personal computer 2 and an optical recorder 10connected to the personal computer 2 via a bus 4. The optical recorder10 comprises an ATAPI (AT attachment packet interface) 12, an encoder14, a digital signal processor 16, a laser drive 18, a read channel 20,a jitter meter 22, a decoder 24, an optical disc 26, a disc motor 28, alaser pickup 30 and firmware 40.

The optical recorder 10 writes data onto the optical disc 26 in thefollowing manner. The personal computer 2 transmits data to be writtenand other relevant control data to the ATAPI 12 of the optical recorder10 via the bus 4. The data is then passed to the encoder 14 forencoding. The encoded data is transmitted to the digital signalprocessor 16 for processing. And the processed data is transmitted tothe laser drive 18 to control the disc motor 28 and the laser pickup 30for writing data onto the optical disc 26.

Data is read from the optical disc 26 in the following manner. Thedigital signal processor 16 sends control signals to the laser drive 18to control the disc motor 28 and the laser pickup 30. The laser pickup30 then reads a radio frequency signal from the optical disc 26. The RFsignal is sent to the read channel 20 for amplification and convertinginto a digital signal. The digital signal is then decoded by the decoder24 and outputted to the personal computer 2 via the ATAPI 12.

Before a piece of data is written onto the optical disc 26, the laserdrive 18 must know the length of the piece of data. And then the laserdrive 18 provides a corresponding write strategy according burningparameters for writing the piece of data onto the optical disc 26. Thewrite strategy needs to be fine tuned according to the material andmanufacturer of the optical disc 26. Otherwise, a false write strategymay cause the optical disc 26 to be unreadable or cause other unexpectedfailures.

The write strategy is fine tuned by writing test data onto a lead-inarea of the optical disc 26 and reading the test data from the lead-inarea before formal data is written onto the optical disc 26. The testwrite process is the same as writing formal data onto the optical disc26. However, the test read process is not identical to reading formaldata from the optical disc 26. After the laser pickup 30 transfers theRF signal to the read channel 20 for processing, the processed RF signalis sent to the decoder 24 for decoding and sent to the jitter meter 22for measuring a difference between the processed RF signal and astandard clock. The difference is then outputted to the digital signalprocessor 16 for calculating the burning quality under the writestrategy used for writing the test data. This information will allow thedigital signal processor 16 to adjust the speeds and positions of thedisc motor 28 and the laser pickup 30 continuously.

Please refer to FIG. 3. FIG. 3 is a block diagram of the jitter meter22. The jitter meter 22 comprises a delay chain 48 formed by N delaycells 42 connected in a cascade manner, a buffer set 44 formed by Nbuffers, and a control unit 46. Each of the delay cells 42 is a Dflip-flop which can either be rising-edge triggered or falling-edgetriggered. Each of the delay cells 42 delays its input signal a timeunit. The N delay cells 42 are used to delay the processed RF signal Ndifferent periods of time. Therefore, the outputs Q of the N delay cells42 will generate delayed RF signals with N different periods of delaytime. The input D of each delay cell 42 is connected to a logic “1”. Theclock input of the first delay cell 42 is connected to the read channel20 for receiving the processed RF signal. The clock input of each of theremaining delay cells 42 is connected to the output Q of a previousdelay cell 42. The control unit 46 has a first input connected to theread channel 20 for receiving the processed RF signal, a second inputfor receiving the standard clock, and an output for outputting a controlsignal. After the processed RF signal changes value, the control signalwill change its value shortly after receiving a falling edge of thestandard clock. The output of the control unit 46 is connected to theclock input (CLK) of the buffer set 44. The outputs Q of the N delaycells 42 are connected to inputs of the N buffers of the buffer set 44.The time for the N buffers to receive outputs of the N delay cells 42 iscontrolled by the control signal outputted by the control unit 46. Whenthe clock input (CLK) of the buffer set 44 is triggered by a change inthe logic value of the control signal, the current logic values of theoutputs Q of the N delay cells 42 will be stored into the N buffers ofthe buffer set 44.

Please refer to FIG. 4. FIG. 4 is a timing diagram of the jitter meter22. The timing diagram include waveforms of the standard clock, theprocessed RF signal, the delayed RF signals, the control signal andlogic values stored in the N buffers of the buffer set 44. The delayedRF signals are illustrated by delay #1 to delay #8. In this case, thebuffer set 44 include 8 buffers. The length of the high potential of theprocessed RF signal represents the length of the test data written ontothe optical disc 26. As shown in FIG. 4, the high potential of theprocessed RF signal crosses three falling-edges of the standard clock,therefore the test data represented by this section of the processed RFsignal is a 3T signal. While a first pulse of the standard clock is at ahigh potential, the processed RF signal changes from a low potential toa high potential. Therefore, the control unit 46 outputs ahigh-potential control signal shortly after receiving a falling edge ofthe standard clock. As soon as the clock input of the buffer set 44receives the high-potential control signal, the buffer set 44 stores an8-bit delay signal transmitted from the eight delay cells 42 of thedelay chain 48. This 8-bit delay signal is named R delay signal. Asillustrated in FIG. 4, when the control signal changes from a lowpotential to a high potential, delay #1 to delay #5 have a logic “1”,delay #6 to delay #8 have a logic “0”, thus R delay signal is“11111000”.

During the fourth pulse of the standard clock, the processed RF signalchanges from a high potential to a low potential. Therefore, the controlunit 46 outputs a low-potential control signal shortly after receiving afalling edge of the standard clock. As soon as the clock input of thebuffer set 44 picks up the low-potential control signal, the buffer set44 stores an 8-bit delay signal transmitted from the eight delay cells42 of the delay chain 48. This 8-bit delay signal is named F delaysignal. As illustrated in FIG. 4, when the control signal changes from ahigh potential to a low potential, delay #1 and delay #2 have a logic“0”, delay #3 to delay #8 have a logic “1”, thus F delay signal is“00111111”.

After the buffer set 44 receives R and F delay signals, these two delaysignals are sent to the digital signal processor 16, and the firmware 40will control the operation of the digital signal processor 16. Thenumber of logic “1” of R delay signal and the number of logic “0” of Fdelay signal are counted and subtracted to find a difference between thetwo numbers. The difference is then mapped to a value between 0 and 1.Since the number of logic “1” of R delay signal is 5, and the number oflogic “0” of F delay signal is 2, the difference between the two numbersis 3, and the mapped value is 0.375 (⅜). This process will be repeatedto find an average difference between the R and F delay signals. If theaverage difference is 2.8, then the digital signal processor 16 willadjust the write strategy according to this average difference. Anaverage difference closer to 0 commonly refers to a better correspondingwrite strategy.

From these calculations, the digital signal processor 16 will determinewhether the write strategy for writing the test data conforms toparameters and arithmetic formula stored in the firmware 40. If so, thejitter meter 22 will no longer be used and the optical recorder 10 canstart to write formal data. If not, the jitter meter 22 will be usedagain until an acceptable write strategy is configured.

In the past, generating an acceptable write strategy used to be acomplicated and time consuming task. Compared to the related art, thejitter meter 22 is installed inside the optical recorder 10. Thereforethe jitter meter 22 can be used to help configuring an acceptable writestrategy for various optical discs easily. And there is no need toconnect the optical recorder 10 to an externally connected jitter meter.

Those skilled in the art will readily observe that numerousmodifications and alterations of the system may be made while retainingthe teachings of the invention. Accordingly, the above disclosure shouldbe construed as limited only by the metes and bounds of the appendedclaims.

1. An optical recording system for burning an optical disc, the opticalrecording system comprising: a housing; a laser pickup installed insidethe housing for writing data onto the optical disc according to a writestrategy and reading an RF signal from the optical disc; a laser driveinstalled inside the housing connected to the laser pickup forcontrolling operations of the laser pickup; a read channel installedinside the housing connected to the laser pickup for processing the RFsignal received by the laser pickup; a jitter meter installed inside thehousing connected to the read channel for generating delay signalsaccording to the processed RF signal; and a digital signal processorinstalled inside the housing connected to the laser drive and the jittermeter for receiving the delay signals, configuring the write strategyaccording to the delay signals, and controlling the laser drive tocontrol the laser pickup to write data onto the optical disc accordingto the configured write strategy; wherein the jitter meter includes: adelay chain having a plurality of delay cells connected in a cascademanner, each delay cell delaying an input signal a time unit; a bufferset connected to the delay chain for storing a delay signal receivedfrom the delay chain, the buffer set having a plurality of buffers eachconnected to a delay cell for receiving a delay bit of the delay signaltransmitted from the delay cell; and a control unit connected to theread channel and the buffer set for outputting a control signalaccording to a standard clock and the processed RF signal.
 2. Theoptical recording system of claim 1 wherein each of the delay cells is aflip-flop.
 3. The optical recording system of claim 2 wherein theflip-flop is either rising-edge triggered or falling-edge triggered. 4.The optical recording system of claim 1 wherein the optical disccomprises a lead-in area, the processed RF signal sent to the jittermeter being generated from an RF signal read from the lead-in area ofthe optical disc.
 5. The optical recording system of claim 1 furthercomprising firmware for storing parameters and arithmetic formula.
 6. Amethod for burning an optical disc in an optical recording systemcomprising the following steps: (a) writing data onto the optical discaccording to a write strategy and reading an RF signal from the opticaldisc; (b) processing the RF signal; (c) generating delay signalsaccording to the processed RF signal by: delaying the processed RFsignal; outputting a control signal according to a standard clock andthe processed RF signal; and generating a delay signal according to thecontrol signal and the delayed RF signals; and (d) configuring the writestrategy according to the delay signals; wherein the delay signal isformed by a plurality of delay bits received from a plurality ofbuffers, each buffer connected to a delay cell from a plurality of delaycells, the plurality of delay cells being connected in a cascade manner.7. The method of claim 6 wherein the RF signal is read from a lead-inarea of the optical disc.
 8. The method of claim 6 wherein the writestrategy in step (d) is configured according to the material andmanufacturer of the optical disc.
 9. An optical recording system forburning an optical disc, the optical recording system comprising: ahousing; a laser pickup installed inside the housing for writing dataonto the optical disc according to a write strategy and reading an RFsignal from the optical disc; a laser drive installed inside the housingconnected to the laser pickup for controlling operations of the laserpickup; a read channel installed inside the housing connected to thelaser pickup for processing the RF signal received by the laser pickup;a jitter meter installed inside the housing connected to the readchannel for generating delay signals according to the processed RFsignal; and a digital signal processor installed inside the housingconnected to the laser drive and the jitter meter for receiving thedelay signals, configuring the write strategy according to the delaysignals, and controlling the laser drive to control the laser pickup towrite data onto the optical disc according to the configured writestrategy; wherein the jitter meter includes: a delay chain having aplurality of delay cells connected in a cascade manner, wherein theprocessed RF signal is coupled to a clock input of a first delay cell,and an output of each delay cell is coupled to a clock input of afollowing delay cell, each delay cell delaying an input signal a timeunit; a buffer set connected to the delay chain for storing a delaysignal received from the delay chain; and a control unit connected tothe read channel and the buffer set for outputting a control signalaccording to a standard clock and the processed RF signal.
 10. Theoptical recording system of claim 9 wherein the buffer set comprises aplurality of buffers each connected to a delay cell for receiving adelay bit of the delay signal transmitted from the delay cell.
 11. Amethod for burning an optical disc in an optical recording systemcomprising: (a) writing data onto the optical disc according to a writestrategy and reading an RF signal from the optical disc; (b) processingthe RF signal; (c) generating delay signals according to the processedRF signal by: delaying the processed RF signal with a delay chain havinga plurality of delay cells connected in a cascade manner, the processedRF signal coupled to a clock input of a first delay cell, and an outputof each delay cell coupled to a clock input of a following delay cell;outputting a control signal according to a standard clock and theprocessed RF signal; and generating a delay signal according to thecontrol signal and the delayed RF signals; and (d) configuring the writestrategy according to the delay signals.
 12. The method of claim 11wherein the delay signal is formed by a plurality of delay bits receivedfrom a plurality of buffers, each buffer connected to a delay cell.